Why Pregnant Women Are More Susceptible to Zika Virus

We know that Zika virus can be especially risky for pregnant women, increasing the risk of birth defects. But a new study from the University of Southern California’s Keck School of Medicine may have insight as to why.

Researchers looked at how the virus affected the blood of healthy men, pregnant women, and non-pregnant women aged 18 to 39. Much like HIV, researchers found that Zika targets the white blood cells that typically swallow up viruses, bacteria, and debris to keep the body healthy.

In expectant mothers, though, virus strains only had to infect 4% of white blood cells to increase immune suppression: An African Zika strain increased suppression by 10% and an Asian strain by 70%.

“Pregnancy naturally suppresses a woman’s immune system so her body doesn’t reject the fetus — essentially it’s a foreign object,” said senior study author Jae Jung, professor and chair of Keck’s department of molecular microbiology and immunology. “Zika exploits that weakness to infect and replicate.”

“The Zika virus vaccines in development seem to be highly effective, but they’re being tested among non-pregnant women with different body chemistry compared to pregnant women,” Jung said.

The mosquito-borne virus is still prevalent in Central and South America, the Caribbean, Central Africa, and Southeast Asia. The CDC maps countries with Zika and is still offering travel warnings and safety guidelines to consider for visits.